protected function log($comment = ''){
    $user = $this->user();
    ORM::factory('Changelog')->vaules(array(
        'user_id' => $user->pk(),
        'section_id' => $user->section->pk(),
        'username' => $user->username.'@'.$user->section->name,
        'time' => time(),
        'uri' => $this->uri($this->request->param(), $this->request->query()),
        'controller' => $this->request->controller(),
        'action' => $this->request->action(),
        'post' => serialize($this->request->post()),
        'comment' => $comment,
    ))->save();
}